JP2011241760A - Motor-driven compressor, heat source machine, and method of controlling the heat source machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor-driven compressor capable of reliably determining the rotating stall and surging without increasing the cost, and a heat source machine and a method of controlling the heat source machine.SOLUTION: The heat source machine 1 has a refrigerating cycle including a motor-driven compressor, a condenser (a water heat exchanger 5), an expansion valve 7 and an evaporator (an air heat exchanger 9), and a control device 15. The motor-driven compressor includes a compressor 3, a motor 11 for driving the compressor 3, and an inverter 17 for driving the motor 11 by the frequency control. The determination unit 42 of the control device 15 calculates the standard current value based on the operational frequency command, and receives the driving current of the motor 11 detected by the inverter 17 side to determine whether the compressor 3 is in a rotating stall state by the comparison with the standard current value.

Description

  TECHNICAL FIELD The present invention relates to a countermeasure technology for turning stall and surging in an electric compressor and a heat source machine, and in particular, an electric compressor, a heat source machine and a control method thereof that can more reliably determine turning stall and surging without incurring an increase in cost. It is about.

  As a heat source device, a compressor, a condenser, an expansion valve, and an evaporator, which constitute a refrigeration cycle in which these are connected via a refrigerant passage, are known. As described above, since the heat source device includes a rotating machine (compressor), the rotating stall and the surging become a problem. Here, the surging phenomenon is caused by an imbalance between the load and the work amount in a relatively low rotation region in the rotating machine. The rotation becomes unstable, the performance drops rapidly, and the vibration and noise of the entire apparatus increase remarkably. Further, the turning stall is a phenomenon in which a part of the annular passage of the rotating machine stalls and this stall region moves at a constant speed in the rotation direction. The surging phenomenon is a self-excited vibration of a drive system consisting of a rotating machine and a pipeline system, and its generation and period depend on the pipeline system, whereas the rotating stall phenomenon is a rotating machine that is unrelated to the pipeline system. It should be noted that these are unstable phenomena, and they are completely different phenomena.

  As a method for coping with the rotating stall of the rotating machine (compressor), for example, there is a “rotating stall preventing device for a compressor” disclosed in Japanese Patent Laid-Open No. 5-340385 (Patent Document 1). In this conventional method, a rotating stall sensor is installed in the flow path of the axial compressor, and the mounting angle of the rectifying blade is changed by an actuator in accordance with a signal from the rotating stall sensor to increase the circumferential speed. The axial flow velocity is increased and the flow is improved to prevent the turning stall.

  Further, as a technique for coping with surging of a rotating machine (blower), for example, there is a “blower surging detection device, detection method, and surging correction method” disclosed in Japanese Patent Laid-Open No. 11-62887 (Patent Document 2). This conventional method collects the driving current of the blower, compares the collected current value with the moving average value of the collected current for a certain period, and determines that the surging state is found when the difference exceeds a predetermined threshold value. And it corrects to a normal state by the opening degree control of the intake valve of an air blower.

JP-A-5-340385 JP-A-11-62887

  However, in the technique disclosed in Patent Document 1 described above, a dedicated sensor and a signal processing circuit attached to the compressor are required for the rotation stall detection of the compressor, which increases the apparatus cost. Moreover, since it is necessary to install a rotation stall sensor in the flow path of a compressor, there also exists a situation that it is difficult to install later.

  In the technique disclosed in Patent Document 2, the surging detection is based on a comparison between the current value and the moving average value of the current in a period that is a certain time back from the current time. Since the value fluctuates from moment to moment, there is a possibility that the surging state may not be detected depending on the setting method for a certain period and how the surging state occurs. Further, since the amplitude of the current fluctuation in the turning stall state is smaller than the amplitude of the current fluctuation in the surging state, the probability that the turning stall is not detected becomes higher.

  The present invention has been made in view of the above-described conventional circumstances, and provides an electric compressor, a heat source apparatus, and a control method thereof that can more reliably determine a rotating stall and a surging without incurring an increase in cost. It is an object.

In order to solve the above problems, the present invention employs the following means.
An electric compressor according to the present invention is an electric compressor including an inverter, an electric motor driven by frequency control of the inverter, and a control unit that instructs an operating frequency command to the inverter. Current detection means for detecting the drive current of the motor, and the control means calculates a standard current value based on the operation frequency command, and compares the standard current value with the current value by the current detection means. It is determined whether or not the electric compressor is in a rotating stall state.

  According to the present invention, the fluctuation of the current value (that is, fluctuation amplitude and fluctuation period) is detected by comparison with a standard current value that is constant unless the operation frequency command is changed. A change in value can be detected, and a turning stall with a relatively small fluctuation amplitude can be determined more reliably. In addition, the drive current detection of the motor on the inverter side is for inverter control and is not a newly added component, and no additional hardware is required to apply the present invention. It does not lead to an increase of.

  Further, according to the present invention, in the electric compressor described above, the control means includes an operation frequency command instructed to the inverter, a voltage-frequency characteristic of the inverter, a suction air volume of the compressor, and a suction of the compressor. The standard current value is calculated based on the pressure and temperature on the discharge side and the pressure and temperature on the discharge side of the compressor.

  Since various quantities used for calculation of the standard current value are various quantities used for operation control of the heat source machine, new hardware addition for applying the present invention is unnecessary, and according to the present invention, It is possible to realize an electric compressor that can more reliably determine the turning stall without increasing the device cost.

  Further, the present invention provides the electric compressor described above, wherein the control means is configured to detect fluctuations in the current value in which the detected current value is a value outside a predetermined range centered on the standard current value. A fluctuation cycle is obtained, and when the fluctuation cycle exceeds a cycle threshold, it is determined that the electric compressor is in a surging state.

  According to the present invention, since the surging state is determined when the fluctuation amplitude of the current value exceeds the amplitude threshold and the fluctuation period exceeds the period threshold, surging can be more reliably determined. Further, it is possible to determine whether the vehicle is in a turning stall state or a surging state based on the same determination method, and the effect that the abnormality detection sequence is easier to understand is also achieved.

  A heat source device according to the present invention is a heat source device having an electric compressor, a condenser, a refrigeration cycle including an expansion valve and an evaporator, and a control means, wherein the electric compressor includes the compressor, An electric motor that drives the compressor; and an inverter that drives the electric motor by controlling the frequency thereof, and the control means calculates a standard current value based on an operation frequency command instructed to the inverter, and the standard current It is determined whether or not the electric compressor is in a rotating stall state by comparing the value with a current value detected by a current detecting means of the inverter.

  According to the present invention, the fluctuation of the current value (that is, fluctuation amplitude and fluctuation period) is detected by comparison with a standard current value that is constant unless the operation frequency command is changed. A change in value can be detected, and a turning stall with a relatively small fluctuation amplitude can be determined more reliably. In addition, the drive current detection of the motor on the inverter side is for inverter control and is not a newly added component, and no additional hardware is required to apply the present invention. It does not lead to an increase of.

  Further, the present invention provides the heat source unit as described above, wherein the control means instructs an operation frequency command to be directed to the inverter, a voltage-frequency characteristic of the inverter, an intake air amount of the compressor, an intake side of the compressor The standard current value is calculated based on the pressure and temperature of the compressor and the pressure and temperature on the discharge side of the compressor.

  Since the various quantities used for the calculation of the standard current value are various quantities used for the operation control of the heat source machine, it is not necessary to add new hardware for applying the present invention. Thus, it is possible to realize a heat source apparatus that can more reliably determine the turning stall without increasing the device cost.

  Further, the present invention provides the heat source unit as described above, wherein when the control unit determines that the electric compressor is in a rotating stall state, the operation frequency command is changed, the expansion valve opening is changed, Changed in the flow rate of the cooling or heating medium supplied to the external load from the condenser or the evaporator, or arranged in a hot gas bypass pipe for leading a part of the refrigerant on the discharge side of the compressor to the suction side The opening degree of the hot gas bypass valve is changed.

For example, any one of these four types of change control, or a combination of two to four types can be performed stepwise to efficiently avoid the turning stall state.
Typically, cold water is used as the cold medium, and hot water is used as the hot medium.

  Further, the present invention provides the heat source apparatus according to the above, wherein the control means is configured to change the detected current value that is out of a predetermined range centered on the standard current value. A cycle is obtained, and when the fluctuation cycle exceeds a cycle threshold, it is determined that the electric compressor is in a surging state, the operation frequency command is changed, the expansion valve is changed, the condenser or the evaporation Of a hot gas bypass valve disposed in a hot gas bypass pipe for guiding a part of the refrigerant on the discharge side of the compressor to the suction side, or changing the flow rate of the cooling medium or the heating medium supplied to the external load from the compressor The opening degree is changed.

According to the present invention, since the surging state is determined when the fluctuation amplitude of the current value exceeds the amplitude threshold and the fluctuation period exceeds the period threshold, surging can be more reliably determined. Further, it is possible to determine whether the vehicle is in a turning stall state or a surging state based on the same determination method, and the effect that the abnormality detection sequence is easier to understand is also achieved. Further, any one of the four types of change control, or a combination of two to four types can be performed stepwise to efficiently avoid the surging state.
Typically, cold water is used as the cold medium, and hot water is used as the hot medium.

  A control method for a heat source apparatus according to the present invention is a control method for a heat source apparatus having a refrigeration cycle including an electric compressor, a condenser, an expansion valve and an evaporator, and a control means, wherein the electric compressor A compressor, an electric motor that drives the compressor, and an inverter that drives the electric motor by controlling the frequency, and calculates a standard current value based on an operating frequency command that is instructed to the inverter. It is characterized in that it is determined whether or not the electric compressor is in a rotating stall state by comparing a current value with a current value detected by a current detecting means of the inverter.

  According to the present invention, the fluctuation of the current value (that is, fluctuation amplitude and fluctuation period) is detected by comparison with a standard current value that is constant unless the operation frequency command is changed. A change in value can be detected, and a turning stall with a relatively small fluctuation amplitude can be determined more reliably.

  According to the present invention, since the fluctuation of the current value is detected by comparison with the standard current value that is a constant value unless the operation frequency command is changed, the fluctuation of the current value can be detected more accurately, and the fluctuation amplitude A relatively small turning stall can be determined more reliably. Further, since new hardware addition for applying the present invention is unnecessary, the apparatus cost does not increase. Further, since the surging state is determined when the fluctuation amplitude of the current value exceeds the amplitude threshold and the fluctuation period exceeds the period threshold, surging can be more reliably determined. Furthermore, as a result of these, there is an effect that it is possible to realize an electric compressor, a heat source unit, and a control method thereof that can more reliably determine the rotation stall and the surging without increasing the cost.

It is a lineblock diagram of the heat source machine (turbo refrigerator) concerning one embodiment of the present invention. It is a flowchart explaining the control method in the heat-source equipment of embodiment.

  Hereinafter, embodiments of an electric compressor, a heat source device, and a control method thereof according to the present invention will be described in detail with reference to the drawings. In the embodiment, the electric compressor, the heat source apparatus, and the control method thereof according to the present invention are applied to a turbo chiller. However, the present invention is not limited thereto, and the electric compressor according to the present invention includes an inverter, The electric compressor driven by frequency control of the inverter is applicable, and the heat source machine and the control method thereof according to the present invention can be applied to the inverter and frequency control of the inverter. Any heat source device having a configuration including an electric compressor provided with an electric motor driven by the above can be applied.

FIG. 1 is a configuration diagram of a turbo refrigerator (heat source machine) according to an embodiment of the present invention.
In the figure, a turbo refrigerator 1 according to this embodiment includes a centrifugal compressor (hereinafter referred to as a compressor) 3 that compresses a gas refrigerant, and a water heat exchanger that condenses the high-pressure gas refrigerant compressed by the compressor 3. A refrigeration cycle comprising: 5; an expansion valve 7 for expanding the high-pressure liquid refrigerant condensed in the water heat exchanger 5; and an air heat exchanger 9 for vaporizing the low-pressure liquid refrigerant expanded by the expansion valve 7. And a control device (control means) 15. The electric compressor referred to in the claims has a configuration including the compressor 3, the electric motor 11, and the inverter 17.
In the figure, although the heating operation which outputs warm water by heat pump operation is shown as an example, this invention is not limited to this, The water heat exchanger 5 shown in FIG. 1 becomes an evaporator, and shows in FIG. The present invention can also be applied to a cooling operation in which the air heat exchanger 9 serves as a condenser and outputs cold water.

  The compressor 3 includes a centrifugal impeller (turbo compression unit) that is rotationally driven by the electric motor 11. An inlet vane 13 for adjusting the refrigerant flow rate is provided at the refrigerant inlet of the compressor 3, and the opening degree of the inlet vane 13 is controlled by the control device 15. A compressor suction temperature sensor 36 for detecting the compressor suction temperature T2 and a compressor suction pressure sensor 37 for detecting the compressor suction pressure P2 are installed on the suction side of the compressor 3. On the discharge side of the compressor 3, a compressor discharge temperature sensor 38 for detecting the compressor discharge temperature T3 and a compressor discharge pressure sensor 39 for detecting the compressor discharge pressure P3 are installed. The sensor signals of the compressor suction temperature sensor 36, the compressor suction pressure sensor 37, the compressor discharge temperature sensor 38, and the compressor discharge pressure sensor 39 are provided to the control device 15.

  Further, the motor 11 is driven by the frequency control of the inverter 17 and the rotation speed of the motor 11 is controlled. The operation frequency is instructed by the operation frequency command from the control device 15. Here, in addition to the semiconductor switching element, the inverter 17 includes an inverter control circuit for generating a PWM signal for controlling the switching operation of the semiconductor switching element, and a drive current detection circuit (V / f control method or vector control). Necessary for inverter control of the system).

Next, the water heat exchanger 5 is provided with a pressure sensor 30 that measures the condensation pressure Pc in the water heat exchanger 5. The sensor signal from the pressure sensor 30 is supplied to the control device 15. Further, the water heat exchanger 5 is provided with cold / hot water acquisition means 21 for obtaining cold / hot water by exchanging heat with the refrigerant in the water heat exchanger 5. An external load such as an air conditioner or a fan coil (not shown) is connected to the cold / hot water acquisition means 21, and warm or cold is supplied to the external load.
A cold / hot water outlet temperature sensor 31 is installed at the cold / hot water outlet of the cold / hot water acquisition means 21, and the sensor signal of the cold / hot water outlet temperature sensor 31 is supplied to the control device 15. Further, on the upstream side of the water heat exchanger 5, a flow rate sensor 35 that detects a flow rate qc of cold / hot water flowing into the water heat exchanger 5, and an inlet temperature T 0 of cold / hot water flowing into the water heat exchanger 5. A cold / hot water inlet temperature sensor 34 is installed. The sensor signals of the cold / hot water inlet temperature sensor 34 and the flow rate sensor 35 are supplied to the control device 15. In the present specification, the cold / hot water means hot water (heat medium) during the heating operation by the heat pump operation shown in FIG. 1, and although not shown, the water heat exchanger 5 of FIG. 1 becomes an evaporator and the air of FIG. During the cooling operation in which the heat exchanger 9 becomes a condenser, it means cold water (cooling medium).

The opening degree of the expansion valve 7 is controlled by the control device 15.
A hot gas bypass pipe (HGBP pipe) 24 is provided between the water heat exchanger 5 and the accumulator 10 described later. The HGBP pipe 24 allows the high-pressure refrigerant gas in the water heat exchanger 5 to flow to the accumulator 10. The HGBP pipe 24 is provided with a hot gas bypass valve (HGBP valve) 25. By adjusting the opening degree of the HGBP valve 25 by the control device 15, the flow rate of the refrigerant flowing in the HGBP pipe 24 is adjusted, and the flow rate of the suction refrigerant gas to the compressor 3 at the time of the low refrigeration capacity is secured.

Next, the air heat exchanger 9 is provided with a pressure sensor that measures the evaporation pressure in the air heat exchanger 9. The sensor signal of this pressure sensor is provided to the control device 15. The air heat exchanger 9 pumps heat from the outside air during heating by the heat pump operation shown in FIG. 1, and exhausts heat to the outside air during the cooling operation as a condenser (not shown).
In the vicinity of the air heat exchanger 9, an accumulator 10 is provided that separates the liquid phase from the refrigerant flowing out of the air heat exchanger 9 and stores the liquid phase thus separated.

  Next, the control device 15 includes a rotation speed control unit 41, a determination unit 42 including a standard current value calculation unit 44 and a cycle determination unit 45, and an avoidance control unit 43. Note that the control device 15 is realized by a processor such as an MPU or a DSP, and each of these components included in the control device 15 is embodied as a functional group of programs executed on the processor.

  The control device 15 performs start control, normal operation control, and stop of the turbo chiller 1 based on state quantities (various sensor signals provided from the various sensors described above), setting parameters, and the like in each part of the turbo chiller 1. Control, abnormal state avoidance control, etc. are performed.

  The rotation speed control unit 41 calculates the chilled / hot water load based on the chilled / hot water inlet temperature T0, the chilled / hot water outlet temperature T1 and the chilled / hot water flow rate qc, the refrigerant flow rate corresponding to the chilled / hot water load, the compressor suction pressure P2, and the compression The inverter frequency of the electric compressor necessary for obtaining the head corresponding to the difference in the machine discharge pressure P3 is determined, and this is instructed to the inverter 17 as an operation frequency command.

  The determination unit 42 calculates a standard current value based on the operation frequency command instructed to the inverter 17 by the standard current value calculation unit 44, and the current value detected by the standard current value and the current detection means of the inverter. To determine whether or not the compressor 3 is in a turning stall state. The period determining unit 43 obtains the fluctuation period of the fluctuation of the current value where the detected current value is out of a predetermined range centered on the standard current value, and the fluctuation period exceeds the period threshold value. Whether or not the compressor 3 is in a turning stall state or a surging state is determined.

In the standard current value calculation unit 44, the standard current value I is calculated by the following equation.
(Equation 1)
I = ρ × Q × (hd−hs) × ηi × ηm / V (f) (1)
Here, ρ is the compressor suction refrigerant density, and is obtained based on the compressor suction pressure P2 and the compressor suction temperature T2. Q is the compressor intake air volume, and is determined from the impeller outer diameter D [m], the flow coefficient φ, and the impeller rotational speed N [rps]. Further, hs and hd are a compressor suction enthalpy and a compressor discharge enthalpy, respectively. The compressor suction enthalpy hs is based on the compressor suction pressure P2 and the compressor suction temperature T2, and the compressor discharge enthalpy hd is the compressor discharge pressure P3. And the compressor discharge temperature T3. Ηi and ηm are inverter efficiency and motor efficiency, respectively, and are set in advance as parameters. Further, V (f) is an inverter voltage, and is obtained from an operation frequency command f instructed to the inverter and a voltage-frequency characteristic (V / f) of the inverter 17.

  The equation (1) indicates that the required power P of the compressor can be calculated as P = ρ × Q × (hd−hs) × ηi × ηm, and on the other hand, the power P is the inverter current I and the inverter voltage V (f). It is derived from the following two relational expressions: (P = V (f) × I).

  The determination of the turning stall in the determination unit 42 is performed as follows. That is, on the inverter 17 side, the drive current detection circuit detects the drive current necessary for inverter control at a predetermined period, but the sampling data is obtained from the inverter 17 as it is, and the obtained current value is the standard current value. Judgment is made based on whether or not I is outside the range of ± 5 [%]. That is, if the current value is out of the range of ± 5 [%] of the standard current value I, it is determined that the compressor 3 is in the rotating stall state.

  The determination unit 42 determines whether the turning stall state or the surging state is based on the fluctuation cycle of the current value. This is because the fluctuation amplitude and the fluctuation cycle of the current value when in the surging state are turned. This utilizes the property that the current value is larger than the fluctuation amplitude and fluctuation period in the stalled state. The fluctuation period will be described in detail. It is known that the fluctuation of the current value in the turning stall state has a frequency that is a factor k (= 0.06 to 1.25) times the impeller rotation speed N. Yes. That is, the stalled portion (1 to 5) moves in the opposite direction relative to the impeller. For example, if the gear ratio of the speed increaser installed between the electric motor 11 and the compressor 3 is 6 and the inverter frequency is 60 [Hz], assuming that the coefficient k = 0.06, 60 × 6 × 0. The vibration frequency is 06 = 21.6 [Hz], and the fluctuation period is 46.3 [msec]. On the other hand, the fluctuation period of the current value in the surging state is several [sec].

  Therefore, the fluctuation cycle (theoretical value) of the current value when the vehicle is in the stalling stall state is calculated in advance, and a larger value may be set as the cycle threshold value. As will be described later, since the contents of the abnormal state avoidance control are switched according to the determination of either the turning stall state or the surging state, the period threshold value may be set in consideration of the contents of the abnormal state avoidance control. desirable.

  Moreover, in the period determination part 43, the fluctuation period (actual value) of an electric current value is calculated | required as follows, for example. That is, the difference between the standard current value I and the current value from the inverter 17 is obtained, zero cross detection is performed on the time series data of the difference, and the time difference from the zero cross point to the immediately following zero cross point is obtained. The fluctuation period can be measured.

  In the case where there is no vibration characteristic due to sudden fluctuations in the current value, the fluctuation cycle of the current value cannot be measured. As such a case, for example, a case where the fluctuation of the current value has a trigger-shaped or step-shaped characteristic is considered, but in the case of the trigger-shaped characteristic, the normal state is immediately returned to the normal state. There is no need for countermeasures, and in the case of the step shape characteristic, the abnormal state is caused by another factor. Therefore, the countermeasure should be left to the abnormal state detection / avoidance control sequence caused by another factor. In other words, if the cycle of the current value cannot be measured by the cycle determination unit 43, it is determined whether or not the step shape characteristic is present. If the step shape characteristic is not obtained, the normal operation control is returned. It is only necessary to shift to another abnormal state detection / avoidance control sequence.

  Summarizing the determination conditions for the abnormal state described above, when the current value is out of the range of ± 5 [%] of the standard current value I and the fluctuation cycle of the current value is below the periodic threshold, the compressor 3 is in the rotating stall state. It is determined that the compressor 3 is in the surging state when the current value is out of the range of ± 5 [%] of the standard current value I and the fluctuation cycle of the current value exceeds the cycle threshold. It becomes.

  As described above, since the fluctuation amplitude of the current value is larger in the surging state than in the turning stall state, for example, the current value has a range of ± 10 [%] of the standard current value I. It may be determined that the compressor 3 is in the surging state when the current value fluctuation period exceeds the period threshold value. In this case, when the current value is in the range of ± 5 [%] to ± 10 [%] of the standard current value I and the fluctuation cycle of the current value is less than the cycle threshold, the compressor 3 is in a rotating stall state. Judge that there is.

  In addition, at least a certain period is required to obtain the fluctuation period of the current value based on the sampling data, and it is not possible to determine whether the vehicle is stalling stalled or surging during the certain period. It will not be possible to move to. As a method for dealing with this, for example, a two-stage cycle threshold (that is, a first cycle threshold and a second cycle threshold; first cycle threshold <second cycle threshold) may be used as a determination condition.

  That is, the fluctuation cycle (actual value) of the current value is compared with the first cycle threshold value for each first fixed period, and if the fluctuation cycle (actual value) of the current value exceeds the first cycle threshold value, the vehicle is not in the surging state but is turned. In parallel with this, the fluctuation period (actually measured value) of the current value is compared with the second period threshold value every second constant period (second constant period> first constant period). If the fluctuation cycle (actual value) of the current value exceeds the second cycle threshold value, it is determined that the surging state is established. By such stepwise setting of the cycle threshold, it is possible to further shorten the period during which the shift to the abnormal state avoidance control is not possible.

  Next, the abnormal state avoidance control by the avoidance control unit 43 will be described. When the determination unit 42 determines that the compressor 3 is in the turning stall state, the avoidance control unit 43 performs stepwise one of the following four types of avoidance control or a combination of two to four types. Do. That is, (1) The inverter frequency of the operation frequency command is increased. (2) Increase the opening degree of the expansion valve 7. (3) Increase the opening of the hot gas bypass valve. (4) Increase the flow rate of cold / hot water. Here, stepwise means adding a change amount in predetermined increments (or multiplying by a change rate in predetermined increments) to determine whether or not the vehicle is in a turning stall state each time. Otherwise, the operation is continued under the operating conditions, and if the vehicle is stalled, further changes are made.

  Further, when the determination unit 42 determines that the compressor 3 is in the surging state, the avoidance control unit 43 performs step by step one of the four types of avoidance control, or a combination of two to four types. Do. However, the increment unit of the change amount (or change rate) is larger in the surging avoidance control than in the turning stall avoidance control.

  Next, the control method in the heat source apparatus provided with each component demonstrated above is demonstrated along the flowchart shown in FIG.

  First, the rotation speed control unit 41 of the control device 15 determines the inverter frequency of the electric compressor, instructs this to the inverter 17 as an operation frequency command (step S101), and performs normal operation control by the control device 15 ( Step S102).

  Further, as soon as the normal operation control is entered, the standard current value calculation unit 44 calculates the standard current value I based on the operation frequency command (step S103). Further, the drive current value detected by the drive current detection circuit sent from the successive inverter 17 is acquired (step S104), and whether or not the acquired current value is out of the range of ± 5 [%] of the standard current value I. Is determined (step S105). If the acquired current value is within ± 5 [%] of the standard current value I, the process returns to step S102 (normal operation control), and the acquired current value is within ± 5 [%] of the standard current value I. If not, the process proceeds to step S106.

  In step S106, the period determination unit 43 obtains a fluctuation period (actually measured value) of the current value based on the sampling data for a certain period, and when the fluctuation period of the current value falls below the period threshold, it is determined that the compressor 3 is in the rotating stall state. When the current value fluctuation cycle exceeds the cycle threshold, it is determined that the compressor 3 is in the surging state.

  When it is determined that the vehicle is in a turning stall state, the process proceeds to step S107 and abnormal state avoidance control by the avoidance control unit 43 is executed. Specifically, (1) increase of inverter frequency of operation frequency command, (2) increase of opening degree of expansion valve 7, (3) increase of opening degree of hot gas bypass valve, (4) flow rate of cold / hot water Any one of these four types of avoidance control, or a combination of two to four types is performed stepwise.

  If it is determined in step S106 that the state is the surging state, the process proceeds to step S108, and abnormal state avoidance control by the avoidance control unit 43 is executed. Specifically, (1) increase of inverter frequency of operation frequency command, (2) increase of opening degree of expansion valve 7, (3) increase of opening degree of hot gas bypass valve, (4) flow rate of cold / hot water Any one of these four types of avoidance control, or a combination of two to four types is performed stepwise. However, the increment unit of the change amount (or change rate) is set to a value larger than that in the turning stall avoidance control.

  As described above, the electric compressor according to the present embodiment includes the electric motor 11 driven by the frequency control of the inverter 17 and the control device 15 that instructs the inverter 17 to provide an operation frequency command. A standard current value based on the operation frequency command is calculated, and the drive current of the electric motor 11 detected on the inverter 17 side is taken in, and it is determined whether or not the electric compressor is in a rotating stall state by comparison with the standard current value. To do. As described above, since the fluctuation of the current value (that is, fluctuation amplitude and fluctuation cycle) is detected by comparison with the standard current value that is constant unless the operation frequency command is changed, the current value is more accurately determined. A fluctuation can be detected, and a turning stall with a relatively small fluctuation amplitude can be determined more reliably. In addition, the drive current detection of the electric motor 11 on the inverter 17 side is for the purpose of inverter control and is not a newly added component, and no new hardware addition is required to apply the present invention. There is no increase in apparatus cost.

  Further, in the electric compressor of the present embodiment, the control device 15 obtains the fluctuation cycle of the fluctuation of the current value at which the detected current value is outside the predetermined range centered on the standard current value, When the fluctuation cycle exceeds the cycle threshold, it is determined that the electric compressor is in a surging state. As described above, since the surging state is determined when the fluctuation amplitude of the current value exceeds the amplitude threshold and the fluctuation period exceeds the period threshold, surging can be more reliably determined. Further, it is possible to determine whether the vehicle is in a turning stall state or a surging state based on the same determination method, and the effect that the abnormality detection sequence is easier to understand is also achieved.

  Further, in the heat source machine (turbo refrigerator 1) and the control method thereof according to the present embodiment, the electric compressor, the condenser (the water heat exchanger 5 in the case of FIG. 1), the expansion valve 7 and the evaporator (the case of FIG. 1). Then, in a heat source device having a refrigeration cycle provided with an air heat exchanger 9) and a control device 15, the electric compressor, the compressor 3, the electric motor 11 that drives the compressor 3, and the frequency control of the electric motor 11 are performed. The determination unit 42 of the control device 15 calculates a standard current value based on the operation frequency command, and captures the drive current of the electric motor 11 detected on the inverter 17 side. Then, it is determined whether or not the compressor 3 is in a rotating stall state by comparison with the standard current value. As described above, since the fluctuation of the current value (that is, fluctuation amplitude and fluctuation cycle) is detected by comparison with the standard current value that is constant unless the operation frequency command is changed, the current value is more accurately determined. A fluctuation can be detected, and a turning stall with a relatively small fluctuation amplitude can be determined more reliably. In addition, the drive current detection of the electric motor 11 on the inverter 17 side is for the purpose of inverter control and is not a newly added component, and no new hardware addition is required to apply the present invention. There is no increase in apparatus cost.

  In the heat source machine (turbo refrigerator 1) and the control method thereof according to the present embodiment, the standard current value calculation unit 44 of the control device 15 instructs the inverter 17 to operate, and the inverter 17 voltage-frequency characteristics. The standard current value is calculated based on the suction air volume of the compressor 3, the pressure and temperature on the suction side of the compressor 3, and the pressure and temperature on the discharge side of the compressor 3. Since the various quantities used for calculating these standard current values are various quantities used for operation control of the heat source machine, no additional hardware is required to apply the present invention, and the cost of the apparatus is increased. Therefore, it is possible to realize a heat source machine and a control method thereof that can more reliably determine the turning stall.

  In the heat source machine (turbo refrigerator 1) and the control method thereof according to the present embodiment, when the compressor 3 is determined to be in the rotating stall state, the avoidance control unit 43 of the control device 15 changes the operation frequency command. Change of the opening degree of the expansion valve 7 or change of the opening degree of the hot gas bypass valve 25 arranged in the hot gas bypass pipe 24 that leads a part of the refrigerant on the discharge side of the compressor 3 to the suction side, cold / hot water Change the flow rate. For example, any one of these four types of avoidance control, or a combination of two to four types can be performed stepwise to efficiently avoid a turning stall condition.

  Further, in the heat source machine (turbo refrigerator 1) and the control method thereof according to the present embodiment, the current value detected by the control device 15 becomes a value out of a predetermined range centered on the standard current value. Regarding the fluctuation, the fluctuation period is obtained, and when the fluctuation period exceeds the period threshold, it is determined that the compressor 3 is in the surging state. As described above, since the surging state is determined when the fluctuation amplitude of the current value exceeds the amplitude threshold and the fluctuation period exceeds the period threshold, surging can be more reliably determined. Further, it is possible to determine whether the vehicle is in a turning stall state or a surging state based on the same determination method, and the effect that the abnormality detection sequence is easier to understand is also achieved.

  In the heat source machine (turbo refrigerator 1) and the control method thereof according to the present embodiment, when the compressor 3 is determined to be in the surging state, the avoidance control unit 43 of the control device 15 changes or expands the operation frequency command. Change of the opening degree of the valve 7 or change of the opening degree of the hot gas bypass valve 25 arranged in the hot gas bypass pipe 24 that leads a part of the refrigerant on the discharge side of the compressor 3 to the suction side, cold / hot water Change the flow rate. For example, by performing any one of these four types of avoidance control, or a combination of two to four types in stages, it is possible to efficiently avoid the surging state.

1 Turbo refrigerator (heat source machine)
3 Compressor 5 Water heat exchanger (condenser)
7 Expansion valve 9 Air heat exchanger (evaporator)
DESCRIPTION OF SYMBOLS 11 Electric motor 13 Inlet vane 15 Control apparatus 17 Inverter 19 Power supply 21 Cold / hot water acquisition means 24 Hot gas bypass piping (HGBP piping)
25 Hot gas bypass valve (HGBP valve)
30, 37, 39 Pressure sensor 31, 34, 36, 38 Cold / hot water outlet temperature sensor 35 Flow rate sensor 41 Rotational speed control unit 42 Determination unit 43 Avoidance control unit 44 Standard current value calculation unit 45 Period determination unit

Claims (8)

An electric compressor comprising: an inverter; an electric motor driven by frequency control of the inverter; and a control means for instructing an operating frequency command to the inverter,
The inverter has current detection means for detecting a drive current of the electric motor,
The control means calculates a standard current value based on the operation frequency command, and determines whether or not the electric compressor is in a rotating stall state by comparing the standard current value with a current value by the current detection means. An electric compressor characterized by that.   The control means includes an operating frequency command instructed to the inverter, a voltage-frequency characteristic of the inverter, a suction air volume of the compressor, a pressure and temperature on the suction side of the compressor, and a discharge side of the compressor The electric compressor according to claim 1, wherein the standard current value is calculated based on a pressure and a temperature of the electric compressor.   The control means obtains a fluctuation cycle of the fluctuation of the current value in which the detected current value is out of a predetermined range centered on the standard current value, and the fluctuation period exceeds a cycle threshold value. The electric compressor according to claim 1, wherein the electric compressor is determined to be in a surging state. A heat source machine having an electric compressor, a condenser, an expansion valve and an evaporator, and a control means,
The electric compressor includes a compressor, an electric motor that drives the compressor, and an inverter that drives the electric motor by frequency control,
The control means calculates a standard current value based on an operation frequency command instructed to the inverter, and compares the standard current value with a current value detected by a current detection means possessed by the inverter. It is judged whether or not is in a turning stall state.   The control means includes an operating frequency command instructed to the inverter, a voltage-frequency characteristic of the inverter, a suction air volume of the compressor, a pressure and temperature on the suction side of the compressor, and a discharge side of the compressor The heat source apparatus according to claim 4, wherein the standard current value is calculated based on the pressure and temperature of the heat source.   When it is determined that the electric compressor is in a rotating stall state, the control means changes the operating frequency command, changes the opening of the expansion valve, and supplies the external load from the condenser or the evaporator. Changing the flow rate of the cooling medium or the heating medium, or changing the opening degree of the hot gas bypass valve arranged in the hot gas bypass pipe that leads a part of the refrigerant on the discharge side of the compressor to the suction side. The heat source machine according to claim 4 or 5, characterized by the above.   The control means obtains a fluctuation cycle of the fluctuation of the current value in which the detected current value is out of a predetermined range centered on the standard current value, and the fluctuation period exceeds a cycle threshold value. In addition, it is determined that the electric compressor is in a surging state, and the operation frequency command is changed, the opening of the expansion valve is changed, or a part of the refrigerant on the discharge side of the compressor is led to the suction side. The heat source apparatus according to any one of claims 4 to 6, wherein an opening degree of a hot gas bypass valve disposed in the hot gas bypass pipe is changed. A control method for a heat source device, comprising a refrigeration cycle including an electric compressor, a condenser, an expansion valve and an evaporator, and a control means,
The electric compressor includes a compressor, an electric motor that drives the compressor, and an inverter that drives the electric motor by frequency control,
A standard current value based on an operation frequency command instructed to the inverter is calculated, and the electric compressor is in a rotating stall state by comparing the standard current value with a current value detected by a current detection means of the inverter. A method of controlling a heat source machine, characterized by determining whether or not there is.

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